The present invention can be used when a user forgets, loses or gets his handset stolen.
For forgotten handsets, call forwarding is standardized, but the user needs to get/borrow a new handset/subscription MSISDN until he/she recovers his/her handset/SIM. He also needs somebody with access to his forgotten handset to manually do the call forwarding process towards the new handset/MSISDN. For outgoing calls, there is no known solution. The user can make calls from his new handset, but receivers will see a different number/MSISDN, not his own.
Document US2006063564 discloses a method for retention of old mobile number on SIM card replacement. It is a SIM OTA based solution to replace one SIM card with another one. The OTA channel is used to update the subscriber data (IMSI/Ki) of the new SIM with the values of the old SIM. However, in this solution the old SIM cannot be reused afterwards (once the user recovers his lost/forgotten SIM), it cannot be activated again.
Document WO2006122871 discloses a method for automatically replacing a user identifying module in a terminal. It describes a solution to replace a SIM card by another one, by replacing its data in the HLR. However, the undo scenario to return to the initial situation (the user recovers his old SIM and can reuse it again) is not supported.
Document U.S. Pat. No. 5,943,620 discloses a method for associating one directory number with two mobile stations within a mobile telecommunications network. It is a HLR based method (non-standard) for keeping two active SIMS associated to one MSISDN number. Although it could be used for SIM replacement (define the replacement SIM as the primary SIM and never try to redirect calls to the lost/replaced SIM), the recovery back to the initial scenario is not described.
Document US2005075137 discloses a method for simplifying the exchange of a SIM card of subscribers of a digital mobile communications network. Again, this is a one-way SIM replacement; the recovery back to the initial scenario is not described.
The present invention provides a solution of all the described problems, offering a solution based on IN or IMS and supporting the recovery back to the initial scenario, when the user recovers his old SIM and can reuse it again.
It is well-known that abbreviations and acronyms are frequently used in the mobile telephony field. Below is a glossary of acronyms/terms used throughout the present specification:    AS Application Server    HLR Home Location Register    HSS Home Subscriber Server    IAM Initial Address Message    IMS IP Multimedia Subsystem    IMSI International Mobile Subscriber Identity    IN Intelligent Network    ISUP ISDN User Part    MNO Mobile Network Operator    MO Mobile Originated    MSC Mobile Switching Centre    MSISDN Mobile Station International Subscriber Directory Number    MSS MSC Server    MT Mobile Terminated    PLMN Public Land Mobile Network    SCP Service Control Point    S-CSCF Serving Call Session Control Function    SDP Service Data Point    SIP Session Initiation Protocol    SMS Short Message Service    SMSC SMS Centre    STP Signal Transfer Point    USSD Unstructured Supplementary Services Data